The present invention relates to a radio frequency IC tag and a method for manufacturing same and more particularly to a radio frequency IC tag having improved structure of an antenna part provided therein and its manufacturing method.
Recently, radio frequency IC tags are widely used for information management or distribution management of articles and structures. Such radio frequency IC tags each include a small IC chip in which information is recorded and a small antenna for transmitting the information recorded in the IC chip by radio and are attached to articles or embedded in structures to be utilized. When information (information concerning attributes of individual articles or structures) recorded in the IC chip is read, a reader/writer is merely held to the radio frequency IC tag to make it possible to communicate with the radio frequency IC tag and read the information recorded in the IC chip without contact.
As such a radio frequency IC tag, the technique disclosed in JP-A-2003-298464 (paragraphs 0067 to 0071 and FIG. 6), for example, is known. In such technique, a microstrip antenna (dipole antenna) including a radiation conductive layer (antenna layer) and a ground layer formed on both sides of a dielectric body is held between a dielectric case made of polypropylene having relatively small dielectric loss. Accordingly, since an antenna part containing an IC chip is covered by a case, the radio frequency IC tag has excellent weather-proof and dust-proof characteristics.
Generally, when the radio frequency IC tag is attached to metal to be used, the communication distance thereof is remarkably reduced due to influence of metal. The technique that the communication distance of the radio frequency IC tag is not reduced even if the tag is attached to metal is disclosed in JP-A-2003-85501 (paragraphs 0010 to 0016 and FIGS. 1 to 3). In the technique disclosed in JP-A-2003-85501, a first antenna is formed through an insulating layer on a conductor constituting the ground and the conductor constitutes a second antenna. A potential difference occurs between the first and second antennas (conductor) due to electrostatic coupling, so that the strength of radio wave radiated by the first antenna is not weakened due to reflection of radio wave by the second antenna and reduction of the communication distance is prevented even if the radio frequency IC tag is attached to metal.